This invention concerns a printed and embossed material, suitable for use as a floor covering and a method and apparatus for making it in a continuous process. More particularly, it concerns a multilayered material combining a base layer, a printed layer and a wear resistant layer, which is embossed in register with the print.
Reverse printed laminates have been made by laminating separate sheets of calendered base material and a preprinted plastic film. Until recently, in continuous processes the printed designs have been limited to random prints because of the difficulty of maintaining the desired dimensions in the preprinted plastic film, in the laminate and in some cases in the base material. The plastic film tends to stretch when it is being printed and subsequently dried. Since it is necessary to apply tension to the printed film during lamination in order to eliminate trapped air and wrinkles, the printed design can also be distorted during lamination.
Alternatively, tiles can be formed in batch processes with designs that are in register to the cut tile by laminating preprinted plastic sheets of silk screen designs to sheets of a suitable base material. The tiles can then be hand clicked from the sheets. The high cost of such a batch process makes in-register printed tile quite expensive and limits its acceptance.
An additional complication is imposed by the desirability of providing a textured surface by embossing the tile. Because the embossing step can be another cause of distortion, some processes are limited to embossing of a plastic surface layer that is integral with a nonplastic stable substrate such as asbestos or asphalt-saturated felt.
As described in U.S. Pat. Nos. 4,312,686, 4,612,074, and 4,773,959, which are incorporated herein by reference, the distortions which occur during printing and laminating are minimized by printing the design on a stable base, preferably release paper, and then transferring the printed design to a hot plastic web made continuously by an extruder. In the printing stage, the plastic web is simultaneously adhered to a carrier belt which moves the web through the printing, laminating and embossing stages. The carrier web supports the web during these steps to avoid distortion thereof. A stress relieved hot plastic film is then laminated to the printed web to provide a protective wear coat. To emboss in register with the printed design, the laminated product is first aligned by means of registration marks as used for alignment during embossing. As a result, individual tiles are cut automatically in register to the printed and embossed pattern.
Although the methods described in the '686, '074, and '959 patents are commercially successful, process lines using these methods still could be improved. One difficulty that may be encountered in operating a continuous process line using these methods arises when transferring the printed design to the sheet material. As indicated above, at the same time the sheet material is adhered to the carrier belt. Simultaneous printing and adhering of the sheet material sometimes produces back-calendering, or the bunching up of the web material, at the printing stage resulting in smearing and elongation of the design.